Daniel, I actually meant punctures of the air springs, which in your installation seem quite unprotected, but I guess that answers the question eloquently thank you.

Well, the casting for the coupler arrived on Friday afternoon.
By yesterday morning the machining was complete and the trailer was trundling around in the park in front of my house. This park is almost a pedestrian thoroughfare, and lots of people ride quad bikes, scramblers and 4x4's on it. It seems to get a lot of use as a driver training venue over the weekends as well. The result is that there are some reasonably good ruts in places, which were taken cross-wise at reasonable speed.

So far, so good, although I have identified a couple of small issues. The rub is of course that, despite filling the water tanks, the trailer is still very light.

Tomorrow evening it is being delivered to a specialist hose supplier for brake pipes.

You will be amazed how quickly the trailer weight increases Peter as you add the box and all the bits on top.
Out of interest the photo of my trailer suspension is taken from the rear ... You will notice that my 150 liter water tank which sits inside the front of the chassis completely protects the air springs from the front!! My main concern there was possible stone damage coming off the rear wheels of the Patrol!!

Hey Peter - I been following this with interest... a very nice project and aI think your design, as usual, is well though through and will be a great success.
I see you plan to have the chassis galvanized - any idea where to do this and the cost. I suppose you remove all bolted on items before galvanizing. Are you just using a spray can for the temp undercoat at the moment?
I test my compression type brakes on my boat trailer either by braking hard and feeling the extra dip in the back of the vehicle when they bite, as this is not evident when they are not braking. You can also brake from a certain speed with and without the brakes engaged and then see the difference in braking distance. I find them very effective even on 3 ton set-up on tow.

I have no idea of where/who yet. I will start asking at Galvaglow in Krugersdorp as they have been doing all my galvanizing for several years now.

Everything will have to be removed first yes.

One idea i found on the net is just to check the temperatures of the brake drums after a longish drive, as i doubt i will be able to feel any difference with this little trailer.

However my real issue is to try and determine if i have my leverage ratios correct. Ie wether the brakes are as effective as possible, working hard when they have to without being too sensitive so that they tend to lock up each time you touch the brakes...

Ie the type of thing the coupler manufacturers need to worry about, and not the user. I am currently not even sure how much it matters as long as they actually provide enough braking, the minimum should to some extent be self-regulating?